1. Field of the Invention
This invention relates to heat-resistant or corrosion-resistant members which can be used, for example, as heat-treating jigs for use in the manufacture of semiconductors and as components of etching equipment used in a process for the manufacture of semiconductors or liquid crystal devices.
2. Description of the Related Art
In the manufacture of semiconductors, heat-treating jigs such as susceptors, liner tubes and wafer boats are being used. Since they come into contact with silicon wafers, they are required to have high purity, excellent thermal shock resistance to rapid heating and rapid cooling, and good chemical stability. Currently, members comprising carbon having SiC laminated thereto by CVD are being used.
Moreover, in the manufacture of semiconductors and liquid crystal devices, halogen-containing (fluorine- or chlorine-containing) corrosive gases having high reactivity are generally used for purposes of etching, film formation and the like. Consequently, high corrosion resistance is required of the parts coming into contact with such a halogen-containing corrosive gas or a plasma thereof, including the inner walls of plasma treatment equipment and jigs such as wafer supports, protective covers and insulating rings. For this reason, such contact parts have conventionally been formed of a material comprising chiefly quartz, Al2O3 or the like.
In recent years, the rates of rapid heating and rapid cooling have been increased in order to enhance the throughput in the manufacture of semiconductors. Consequently, the conventionally used members (comprising a carbon substrate having SiC laminated thereto by CVD) have posed problems, for example, in that they may fail to exhibit a good thermal response or they may be damaged by a thermal shock. Accordingly, there have been proposed a member in which an intermediate layer of SiC-C is disposed between the carbon substrate and SiC in order to lessen thermal shocks (Japanese Patent Provisional Publication No. 11-130565/""99) and a member in which the conditions of CVD and the properties of carbon are controlled so as to control the properties of SIC and thereby improve thermal shock resistance (Japanese Patent Provisional Publication No. 2000-302577). However, the aforesaid members are still insufficient in thermal shock resistance and corrosion resistance.
In order to further enhance the integration density of semiconductor circuit devices, halogen-containing corrosive gases having higher reactivity than conventional gases have come to be used during plasma processing. The conventionally used materials comprising chiefly quartz, Al2O3 or the like have insufficient corrosion resistance to such gases and, therefor, have posed problems in that their gas contact surfaces are etched to undergo a change in surface properties, and in that their transparency is reduced to cause an increase in rejection rate.
In order to solve these problems, compound oxides of rare earth elements and Al (e.g., YAG (Y3Al5O12)), silicate compounds and the like have been proposed for use as members having excellent corrosion resistance to halogen-containing corrosive gases or plasmas thereof (see Japanese Patent Provisional Publication Nos. 10-45461/""98, 10-45467/""98 and 11-157916/""99). Although the corrosion-resistant members described in the aforementioned patents have excellent corrosion resistance, they are sintered bodies and hence have the disadvantage that their mechanical strength is not sufficient to produce large members.
In Japanese Patent Provisional Publication No. 10-45461/""98, it is described that compound oxides of rare earth elements and Al have excellent corrosion resistance to halogen-containing corrosive gases. However, sintered bodies made of such compound oxides of rare earth elements and Al are low in mechanical strength (in particular, toughness) and hence have the disadvantage that they may be broken during handling. For this reason, they have not been put to practical use. Moreover, in Japanese Patent Provisional Publication No. 2000-191369, it is described that, among compound oxides of rare earth elements and Al, RE3Al5O12 (in which RE represents a rare earth element such as Y) having the garnet structure is most excellent in corrosion resistance to halogen-containing corrosive gas plasmas. However, sintered bodies made of such compound oxides of rare earth elements and Al having the garnet structure have the disadvantage that their mechanical strength is especially low.
An object of the present invention is to provide excellent members which have high purity, good thermal shock resistance and high mechanical strength and which are useful, for example, as heat-treating jigs for use in the manufacture of semiconductors and components of etching equipment used in a process for the manufacture of semiconductors or liquid crystal devices.
The present inventors made intensive investigations with a view to solving the above-described problems. As a result, it has been found that oxides composed of a rare earth oxide and Al2O3 in a specific proportion have the most excellent corrosion resistance. The present invention has been completed on the basis of this finding.
The present invention provides a rare earth-containing oxide member comprising a substrate comprising at least one selected from group consisting of C, Si, Al, Ni, Ti, Fe, Mo, Ta and W, or an alloy comprising at least one selected from group consisting of Si, Al, Ni, Ti, Fe, Mo, Ta and W; and a compound oxide laminated to the substrate, the compound oxide comprising a rare earth element (inclusive of Y) and Al and having a composition of 40 to 90 mole % of rare earth oxide and 10 to 60 mole % of Al2O3, based on the total amount of the oxides. The present invention also provides a heat-treating jig using such a rare earth-containing oxide member wherein the total amount of iron family elements, alkali metal elements and alkaline earth metal elements is not greater than 20 ppm.